1. Field of the Invention
The present invention relates generally to an enclosed measuring device. The invention relates particularly to a device for measuring the relative position of two objects which are movable relative to each other, particularly for the measurement of lengths or angles. The device includes a housing connected to one of the objects. The housing defines at least one slot extending in the direction of movement of the two object relative to each other. A pair of flexible cover members attached to the housing so as to cover the slot extend in the direction of the slot. The two cover members contact each other and are shaped in such a way that a labyrinth-type line of contact is formed between the two cover members. A carrier member attached to the other one of the objects extends through the slot and between the two cover members. The carrier member is shaped to conform to the line of contact between the two cover members. A structural unit serving for carrying out the measurement is attached to the end of the carrier member.
2. Description of the Prior Art
In enclosed measuring devices of the above-described type, it is necessary to provide a longitudinal slot in the housing through which the carrier member can extend into the interior of the housing, so that the structural unit used for scanning the scale located within the housing can be connected to a mounting base provided outside of the housing. For example, in the case of a machine with bed and sliding carriage, the relative movement of the bed and the sliding carriage is transmitted to the scale or the structural scanning unit and the carrier member is moved within the slot in the direction of the relative movement and the movement can thus be measured.
In order to provide protection for the highly sensitive scale, the slot formed in the housing must be closed as effectively as possible. A passage toward the interior of the housing should be made available only in the area of the carrying member.
A measuring device of the above-described type is disclosed in German Pat. No. 28 46 768. In this measuring device, a scale and a scanning unit are mounted in a hollow member which is provided with a continuous slot in measuring direction. This slot is closed by means of sealing elements arranged in a roof-like manner, the sealing elements being formed by lips of plastics material or rubber. A carrying member extends through the sealing elements in order to connect the scanning unit to an object to be measured.
Moreover, German Pat. No. 34 09 514 discloses an enclosed measuring device in which an especially effective protection against sprayed media is obtained by sealing elements which have a labyrinth-type shape in transverse cross-section. The shape of the carrying member conforms to the labyrinth-type shape of the sealing elements, so that the sealing effect is maintained even where the carrying member extends through the sealing elements.
It is the object of the present invention to further improve the sealing members used for sealing the longitudinal slot of the housing of the measuring device described above.